[Meremoth]

  Yes, there are 3.5mm to 6.3mm adapters available. There are two main kinds, as you can see in the following links. You will want a 3.5mm female to 6.3mm male. Despite what some may tell you, realistically you won't notice any degradation of the sound quality.
 
http://www.amazon.com/iMBAPrice%C2%AE-Premium-Quality-Adapter-STEREO/dp/B00BE50BPO/ref=sr_1_3?ie=UTF8&qid=1431987766&sr=8-3&keywords=3.5mm+to+6.3mm
http://www.amazon.com/igloon-TM-Headphone-Extension-Headphones/dp/B00MP62SI4/ref=sr_1_16?ie=UTF8&qid=1431987766&sr=8-16&keywords=3.5mm+to+6.3mm
 
 
I think it's safe to say the AD900X are pretty efficient too based on the specs and the fact that you can listen to them comfortably on an iPad. I would probably check with JDS Labs or another owner of the headphone/amp combo for their opinion on whether you should go low or medium gain, as I don't have direct experience and would hate to lead you wrong.
With that said, about 50%-60% of the amps I've owned give a very slight background hiss with my TH900. Not a problem when music is playing, but it drives me crazy on quiet passages or between songs.
 
The O2+ODAC is a combo unit that has both the DAC and amp in one, so actually all you need is a USB cable to connect the device to your computer. If you think you might want to hook this up to a different amp in the future, I would say the rear RCA line-outs would be a good thing to add on. I'm not sure how much extra it costs, but it would be a nice future-proofing thing if it's not much more.

 
Another Head-Fi member suggested I get separate units, the standalone O2 and the standalone ODAC, instead of the O2+ODAC combo, so I can use the amp and DAC with different amps and DACS in the future, if I ever purchase a different amp and DAC on down the line.  With that in mind, what additional components will I need?  Should I just get the connectors, adaptors, cables, etc. from JDS, or should I get them from somewhere else?  Are the cables/connectors/adapters from JDS good quality?

The RCA line-outputs for the ODAC is an additional $30.  Why would getting RCA line-outputs be considered 'future-proofing' vs 3.5mm?  
 
Thanks again for all your help!  

 

[Sonic Defender]

sigh
yep

Now now, I said my bad. We all read post incorrectly from time to time.

 

[Sonic Defender]

   
Another Head-Fi member suggested I get separate units, the standalone O2 and the standalone ODAC, instead of the O2+ODAC combo, so I can use the amp and DAC with different amps and DACS in the future, if I ever purchase a different amp and DAC on down the line.  With that in mind, what additional components will I need?  Should I just get the connectors, adaptors, cables, etc. from JDS, or should I get them from somewhere else?  Are the cables/connectors/adapters from JDS good quality?

The RCA line-outputs for the ODAC is an additional $30.  Why would getting RCA line-outputs be considered 'future-proofing' vs 3.5mm?  
 
Thanks again for all your help!  

Separates are never bad to consider. More flexible keep one, sell one, try different combinations, sell both etc.

 

[Meremoth]

  The noise you hear during quiet passages also depends on the recording rig. Older analogue recordings are typically noisy where I find contemporary recordings can be much blacker background. Beyond that the amps signal to noise comes into play, but I suspect the O2 is decent. If you don't listen to music with very wide dynamic swings, really quiet passages for any real period of time even a slightly noisy amp may not bother you. But as was mentioned, the TH900 are sensitive so if you do like very quiet passages in your music you need to understand that if the recordings are also fairly noisy you are going to hear hiss.
 
I haven't noticed any issue with the TH900 so far, but I don't really listen to older recordings anymore, at least not very often preferring electronic music these days. I would also get the RCA out option. The more flexibility you pay for the better, eventually you're going to sell the gear and more options = more potential buyers. I can't imagine any adapter resulting in sound quality degradation that you could hear. Let us know how things go for you.

 
So the lower the gain, the less the potential for a hiss, yeah?  

So, seeing how the 900X's and TH-900's are easy to drive, Low (1.0x, 2.5x) should be the best, yeah?  Or should I do Medium (1.0x, 3.5x) just to be safe?  If Medium introduce a hiss vs. Low, how noticeable would it be?
 
Thanks.  

 

[Sonic Defender]

   
So the lower the gain, the less the potential for a hiss, yeah?  

So, seeing how the 900X's and TH-900's are easy to drive, Low (1.0x, 2.5x) should be the best, yeah?  Or should I do Medium (1.0x, 3.5x) just to be safe?  If Medium introduce a hiss vs. Low, how noticeable would it be?
 
Thanks.  

I would ask JDS Labs directly, but I would think medium gain a safe position. You may want more gain for a tougher to drive/less sensitive headphone in the future. But yes, gain does bring with it some noise, but really under most listening situations if the amp is decent the noise shouldn't be a factor except in the conditions discussed above.

 

[Sonic Defender]

@StanD, what do you say about the gain situation here?

 

[earthpeople]

   
Another Head-Fi member suggested I get separate units, the standalone O2 and the standalone ODAC, instead of the O2+ODAC combo, so I can use the amp and DAC with different amps and DACS in the future, if I ever purchase a different amp and DAC on down the line.  With that in mind, what additional components will I need?  Should I just get the connectors, adaptors, cables, etc. from JDS, or should I get them from somewhere else?  Are the cables/connectors/adapters from JDS good quality?

The RCA line-outputs for the ODAC is an additional $30.  Why would getting RCA line-outputs be considered 'future-proofing' vs 3.5mm?  
 
Thanks again for all your help!  

 
If you decide to go with separates, you'll just need an additional cable to connect the two. Just have to match up the output connector (whether it's RCA, 3.5mm, etc) on the DAC with the input connector on the amp. 
 
I suppose if the amp already has 3.5mm DAC line-out, you don't necessarily need RCA because you can always get an adapter if necessary. I just recommend RCA because it is one of the most common and standard audio connectors. But yes, you can always get a 3.5mm to RCA cable if you need to connect the DAC to something else. 
 
On the background noise issue, yes it can depend on the recording but what I was talking about specifically is just the noise from the amp, meaning even when no music is playing. I don't mean to scare you with this and like Sonic Defender says, it likely won't be a problem at 3.5x nor will it be a problem while music is playing. I'm not sure if there's a way to math out whether you'll get hiss or not, but if there is I would very much like to know for my own future purchases! Even if you do get it, it's a very low level hiss in pretty much every case.

 

[up late]

@meremoth - dac/amp combos are ideal for computer based headphone listening. less cable clutter and usually smaller footprints than separate components.

 

[Meremoth]

Thanks again, Sonic and earthpeople, you guys have been fabulous.  I'll contact JDS Labs about the gain, but I really love/appreciate reading y'alls opinions on the matter(s).
 
 
@up late - That is what I was originally going to get, but a couple of people said it would be better to get separate units because I could use them with other amps and DACs in the future if I decide to mix and match, but I don't plan on getting another DAC or amp for many years after purchasing these.    Also, I was told that both the ODAC and O2 are relatively small.  
 
Is there any benefit to the combo all-in-one unit vs separate units except for less clutter/more space/less footprint?  Any sound quality difference at all, even in the slightest?  
 
 
Thanks again guys.  

 
 
I would 'like' y'alls posts, but it said I have reached my limit for giving posts the thumbs up.  

 

[AudioMan2013]

Thanks again, Sonic and earthpeople, you guys have been fabulous.  I'll contact JDS Labs about the gain, but I really love/appreciate reading y'alls opinions on the matter(s).


@up late
 - That is what I was originally going to get, but a couple of people said it would be better to get separate units because I could use them with other amps and DACs in the future if I decide to mix and match, but I don't plan on getting another DAC or amp for many years after purchasing these.    Also, I was told that both the ODAC and O2 are relatively small.  

Is there any benefit to the combo all-in-one unit vs separate units except for less clutter/more space/less footprint?  Any sound quality difference at all, even in the slightest?  


Thanks again guys.  :bigsmile_face:


I would 'like' y'alls posts, but it said I have reached my limit for giving posts the thumbs up.  :mad:

Depends on your budget. Id go for an Oppo HA-1.

 

[Meremoth]

Depends on your budget. Id go for an Oppo HA-1.

 
Are you recommending me the Oppo HA-1 to go with the ODAC and TH-900's?  

$1200 is a lil rich for my blood for an amp, especially considering I'll already be dropping that much for the TH-900's, but I do appreciate the recommendation.  

 

[AudioMan2013]

Are you recommending me the Oppo HA-1 to go with the ODAC and TH-900's


$1200 is a lil rich for my blood for an amp, especially considering I'll already be dropping that much for the TH-900's, but I do appreciate the recommendation.  

The HA-1 is a dac/preamp/amp. It works well in a home setup as well.

 

[up late]

Thanks again, Sonic and earthpeople, you guys have been fabulous.  I'll contact JDS Labs about the gain, but I really love/appreciate reading y'alls opinions on the matter(s).


@up late
 - That is what I was originally going to get, but a couple of people said it would be better to get separate units because I could use them with other amps and DACs in the future if I decide to mix and match, but I don't plan on getting another DAC or amp for many years after purchasing these.    Also, I was told that both the ODAC and O2 are relatively small.  

Is there any benefit to the combo all-in-one unit vs separate units except for less clutter/more space/less footprint?  Any sound quality difference at all, even in the slightest?  


Thanks again guys.  :bigsmile_face:


I would 'like' y'alls posts, but it said I have reached my limit for giving posts the thumbs up.  :mad:

you would need to compare components to determine if you could actually hear a difference, otherwise all you can go by is other folks opinions and manufacturers claims.

a combined dac/amp like the one you originally had in mind looks fine to me.

 

[Meremoth]

The HA-1 is a dac/preamp/amp. It works well in a home setup as well.

 
Oh, cool.  Still, that'd be $1200 vs ~ $345 for the customized ODAC and O2.  I want a mostly neutral/transparent amp and DAC.  I prefer most of my color to come from the headphones.  What would you consider the HA-1, as far as neutrality, transparency, coloration, etc. is concerned?
 
Also, will there be a benefit for me (TH-900 + PC) of having a preamp?  Do active preamps really help amps and DAC's out that much and does that 'help' result in better sound quality?
 

you would need to compare components to determine if you could actually hear a difference, otherwise all you can go by is other folks opinions and manufacturers claims.

a combined dac/amp like the one you originally had in mind looks fine to me.

 
 
I'm indecisive to a fault.  Even if I could compare and listen to all this equipment (which I cannot, unfortunately), I would still ask for y'alls opinions.  
 
So, in your opinion, does having the O2 + ODAC combined into one unit offer any advantage sonically vs. the stand-alone units?  
 
 
 
Thanks guys.

 

[Zojokkeli]

If anything, the combined unit might sound worse than separate dac and amp, but realistically there's probably not a huge a difference.
I was also going to recommend something more expensive than O2+ODAC, but if you are new to the audio there's no reason to dive deep into the rabbit hole immediately. It's always best to get the best headphones you can afford, and worry about the rest of the chain later.